Sheehan is arguably is best known for television roles such as Nathan Young in the very popular British show Misfits and as Darren in Love/Hate, as well as the 2009 film Cherrybomb alongside Rupert Grint.

His casting in Mortal Engines is one step towards being a massively popular actor, especially if Mortal Engines is a success and spawns sequels based on the four novels that feature Tom and Hester.